1. Field of the Invention
The present invention relates to a linear oscillatory actuator that, for example, can be used as a drive source of an electric shaver.
2. Description of Related Art
A conventional linear oscillatory actuator is disclosed in a Patent Document 1 (Japanese Patent Application Laid-Open No. 2005-354879). As shown in FIGS. 7 to 9, this linear oscillatory actuator 50 includes a stator block 51 having an electromagnet 52, two moving elements 60 each having a permanent magnet 61 disposed oppositely to the electromagnet 52, two pairs of connecting plates 70 that connect the moving elements 60 with the stator block 51, respectively, and a pair of coupling spring portions 80 that couple the two moving elements 60.
Magnetic pole faces of the electromagnetic 52 in the stator block 51 are disposed at a position opposite to the permanent magnets 61 in the two moving elements 60.
Each of the moving elements 60 includes a moving-side housing 64, and is integrally formed with the pair of connecting plates 70 so as to reciprocate independently in its reciprocating direction (M direction) due to deflection of the pair of connecting plates 70. Both of the permanent magnets 61 of the moving elements 60 are disposed oppositely to the magnetic pole faces of the electromagnet 52 in the stator block 51 with a predetermined gap therebetween. One of the permanent magnet 61 is disposed in reversed polarity to another of the permanent magnet 61, so that they are subject to opposite magnetic forces (an attractive force and a repelling force) caused by a magnetic field produced by the electromagnet 52, respectively. Therefore, opposite drive forces apply to the moving elements 60 in the reciprocating direction (M direction), respectively, when the electromagnet 52 is activated.
The connecting plates 70 in a pair are disposed at both ends of the moving element 60, respectively. The connecting plates 70 are integrally formed with the moving-side member 64 of the moving element 60. Each of the connecting plates 70 includes an upper extending portion 73, a lower extending portion 74, and an elastic planar portion 71 that is formed between the extending portions 73 and 74. The connecting plates 70 are elastic suspensions for supporting the moving element 60. The upper extending portion 73 connects with the moving housing 64, and the lower extending portion 74 connects with a fixed-side base 54 of the stator block 51. The elastic planar portion 71 consists of two spring plates 71a and 71b that are aligned parallel to each other with a predetermined distance, and connects the upper extending portion 73 with the lower extending portion 74. A continuous portion 76 between the upper extending portion 73 and the spring plates 71b (the elastic planar portion 71) is formed into a simple curved shape with a small curvature, as shown in FIGS. 7 and 8.
Each of the coupling spring portions 80 has a C-ring shape and is connected with the pair of moving elements 60 only at its both ends, respectively. Each of the coupling spring portions 80 has a symmetrical shape in a center plane between the pair of moving elements 60.
In the above configuration, polarity generated on the magnetic pole faces of the electromagnetic 52 is changed alternately after the electromagnetic 52 is activated. As a result, the drive forces opposite to each other are generated due to electromagnetic forces between the electromagnetic 52 and the permanent magnets 61, and apply to the pair of moving elements 60 alternately. Therefore, the pair of moving elements 60 reciprocates due to deflection of the connecting plates 70 with opposite phase. In addition, the coupling spring portions 80 apply elastic restoring forces to both of the moving elements 60 to restrict oscillation of the moving elements 60. As a result, fluctuation in the oscillation of the pair of moving elements 60 is restricted, so that the pair of moving elements 60 reciprocates with predetermined constant amplitude.